In a NAND flash memory, all bit lines must be charged at the beginning of a program operation, and all the bit lines must be likewise charged and currents flowing through all the bit lines must be judged at the beginning of a verify operation. Therefore, a very large current is required, and a large peak current is temporarily generated.
Further, the NAND flash memory is often used as a multichip package (MCP) in which a plurality of, e.g., two to four chips are mounted at the same time or a memory card in which a plurality of chips are mounted in order to increase a memory capacity. In case that the plurality of chips are mounted in this manner, when peak currents in the respective chips overlap, a larger peak current is generated, and a consumption current is increased.